On Jan 17, 2010, at 8:17 PM, maiya wrote:
There must be a very basic thing I am not getting...
I'm working with some entropy functions and the convention is to use
log(0)=0.
I suppose the outcome of that effort may depend on whether you have
assumed the needed godlike capacities to change the laws of
mathematics. But I suppose that as the Earth mother that might occur
to you. Go ahead, define a new mathematics.
--
David
So I wrote a function:
llog<-function(x){
if (x ==0) 0 else log(x)
}
which seems to work fine for individual numbers e.g.
llog(0/2)
[1] 0
but if I try whole vectors or tables:
p<-c(4,3,1,0)
q<-c(2,2,2,2)
llog(p/q)
I get this:
[1] 0.6931472 0.4054651 -0.6931472 -Inf
What am I missing?
Thanks!
Maja
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
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